Vibrator power supply



Feb. 27, 1951 'T. P. DILLON 2,543,232

VIBHATQR POWER SUPPLY Filed Dec. 22, 1949 Snnentor 72mm; 9.27am

Patented Feb. 27, 1951 UNITED STATES PATENT OFFICE "IBRATOR POWER SUPPLY Thomas P. Dillon, Yeadon, Pa., assignor to Radio Corporation of America, a corporation of Delaware Application December 22,1949, Serial No. 134,516

Claims.

ondary voltage step-up winding of the transm former, and this secondary voltage usually is rectified to provide a relatively high voltage direct current output.

One of the principal difficulties encountered in such power supply systems arises from the fact that when the vibrator first is energized, the oscillations of the reed do not immediately build up to their normal full amplitude and frequency. As a result, the contact between the reed and the transformer primary sections lasts somewhat longer than during normal operation, so that the current from the voltage source through the transformer primary and the reed contacts reaches an excessive value. When the contacts of the vibrator open, an excessive counter electromotive force is set up which causes arcing and rapid deterioration of the contacts.

To avoid this difficulty, it has previously been proposed to connect a current limiting resistor in series between the transformer primary wind ing and the low voltage source, and to provide a relay having its operating winding energized by the low voltage source to actuate a pair of contacts for short-circuiting the current limiting resistor after the vibrating reed has reached normal oscillating condition (see e. g. U. S. Patent 2,435,515). While this expedient has proved helpful in alleviating the difficulty, it has been found that the amount of delay which can be "built in to a relay is not suflicient to protect the vibrator contacts fully. For example, the maximum delay action that can be conveniently provided in conventional relays may be of the order of 1 or 1 seconds, while the time required for the vibrating reed to reach full oscillation may be of the order of 4 or 5 seconds. Consequently, the foregoing expedient sometimes is not adequate to provide full protection of the vibrator contacts.

' It is, accordingly, a principal object of the present invention to provide an improved arrange- 2 ment for protecting the contacts of a vibrator in a power supply system.

A further object of the invention is to provide an improved vibrator power supply system.

In accordance with the invention, the foregoing and other related objects and advantages are attained in a vibrator power supply system having a thermionic rectifier tube in the output section thereof, and with a relay, controlled by the output current of the system, for short-circuiting a current limiting resistor in the input circuit. In such an arrangement, the relay will remain inoperative until sufficient time has elapsed for the electron emitter in the thermionic rectifier tube to become heated to operating condition, thereby adding the heating time of the rectifier to any 2 delay time inherent in the relay operation and insuring that the vibrator reed will be operating normally before the protective resistor is removed from the circuit. Also, the relay winding can be utilized as an inductance element in a filter circuit, thereby reducing the total number of parts required.

A more complete understanding of the invention can be had by reference to the following description of an illustrative embodiment thereof,

when considered in connection with the accompanying drawing, the single figure of which is a schematic diagram of a power supply system arranged in accordance with the present invention.

The apparatus shown in the drawing comprises a multiple output vibrator power supply providing 4 different output voltages to load circuits, shown schematically as resistors R1, R2, R3, R4, from a single relatively low voltage source. Such a systemmay be used to advantage in connection with a combined transmitter-receiver apparatus, for example. A pair of input terminals it] are adapted to be connected to a low voltage direct current source (not shown) to energize a relatively low voltage electromechanical vibrator I2 and a relatively high voltage vibrator 14 through an input lead E6. The return connections to the terminals in are shown by conventional ground" symbols.

The vibrator 42 comprises a reed actuating coil l8 connected to the input lead It, two pairs of contacts 20, 22, which are connected to theend terminals of the center-tapped primary winding 24 of a transformer 25, and a reed 28 which is adapted alternately to ground the end terminals of the two primary winding sections through the contacts 20, 22 upon actuation of the reed 28.

The center tap 30 of the primary winding 24 is connected to the input lead l6 through a current limiting resistor 32, and a capacitor 34 is connected acros the transformer primary winding 24 to serve as a buffer in reducing arcing during normal operation of the vibrator I2.

The transformer 26 is provided with three secondary windings 36, 38, and 40, across each of which alternating voltages are developed during normal operation of the system. One of the windings, 35, is connected across a full wave rectifier bridge 42 to provide a very low voltage direct current through a filter network 44. The second econdary winding, 38, is a voltage step-up winding connected to the anodes 4B, 48 of a thermionic rectifier 50, and a center tap 39 of the winding 38 is connected to the cathode 49 of the rectifier 50 through ground so that the rectifier 50 is connected for full wave rectification. The other secondary winding 43 of the transformer 26 is connected across the heater-filament 52 of the rectifier 50 in order to heat the electron emitting cathode 49.

A relay 54 has an operating winding 56 connected in circuit with the rectifier 50, and is provided with two sets of contacts 58, 60 which are adapted to close in response to current fiow through the relay winding 56. The contacts 58 are connected across the current limiting resistor 32 so that the resistor 32 will be short-circuited upon energization of the relay 54, while the contacts 58 are connected to perform a similar function in a portion of the apparatus to be described hereinafter. In accordance, with an important feature of the invention, a pair of capacitors 62, 64, together with the relay Winding 56, form an L-C smoothing out ripples in the rectified voltage developed by the tube 50.

In the portion of the apparatus thus far described, when a low voltage direct current source, say of the order of 24 volts, is connected to the terminals ID, the reed I8 will be in its rest position, as shown, touching the contacts 20. This will allow current to fiow through the coil I8, drawing the reed away from the contacts 20, and

breaking the circuit through the coil I8. The

reed I8 then will return to the contacts 20, and repetition of the same action soon will cause the reed alternately to touch the contacts 20, 22, thereby causing current to flow alternately through the two sections of the primary winding 24. During the first several cycles of operation of the reed, the current limiting resistor 32 will hold the current flowing through the contacts 29, 22 to a value sufficiently small to prevent excessive arcing between the reed and the contacts. The alternate flow of current through the transformer primary winding sections will produce an alternating voltage across the secondary windings 35, 38 and 40, and after a few seconds the cathode 49 of the tube 50 will be heated suificiently by the filament 52 to allow current to flow in the tube 50. Thereupon, the relay 54 will be energized, closing the contacts 58, 60, and short-circuiting the resistor 32, so that full current can flow through the primary winding 24 of the transformer 26. Inasmuch as the contacts 58 cannot close until after the tube 50 becomes conductive, the current limiting resistor 32 will remain in the circuit long enough to insure that the reed 28 will have reached normal oscillating conditions before the resistor 32 is removed from the circuit. Consequently, arcing at the contacts 20, 22 due to excessive current flow therethrough will be positively pre-- vented during the warm-up time of the tube 60.

filter network for 4 and this time interval will be more than sumcient to allow the reed I8 to reach normal oscillation.

The high voltage vibrator I4 is connected in a circuit quite similar to that already described for the vibrator I2, with the exception that the vibrator I4 is provided with an auxiliary starting contact I2I, and a capacitor 66 and a resistor 53 are connected between the contact I2I and ground to reduce hash voltages generated due to slight arcing which may occur at the starting contact I2I. A current limiting resistor I32 is connected between the input lead I6 and the primary winding I24 of a transformer I25 to reduce the initial input current to the vibrator I4.

The contacts 60 of the relay 54 are connected to short-circuit the resistor I32 in the manner already described for the resistor 32. The output circuits for the section of the apparatus energized by the vibrator I4 correspond to those already described for the section energized by the vibrator I2, with the exception that an inductor I0 is connected in the filter circuit for the thermionic rectifier I50, rather than a relay winding as in the filter circuit for the rectifier 50.

It can be seen that the apparatus described embodies means for protecting the contacts in each of two vibrator circuits during initial energization of the vibrators, and that the delay provided by the heating time of the electronemitting electrode in a thermionic rectifier will insure protection of the vibrator contacts beyond the time provided by any delay action of a relay alone. Also, it is evident that the arrangement shown can be used to particular advantage where a cold-cathode rectifier and a thermionic rectifier are used with separate vibrators in the same power supply system, since the delay time provided by the thermionic rectifier can be utilized to protect both vibrators. It will, of course, be understood that any number of vibrators in a power supply system can be protected with a single relay connected in the manner shown and described herein. A further feature to be noted resides in the saving of an element in the filter for the thermionic rectifier, since the relay winding can be used in place of the usual inductor in the filter.

What is claimed is:

1. In a power supply system, in combination, a transformer having a primary winding and a secondary winding, a voltage input network comprising (1) a pair of input terminals, (2) a r sistor connected between a terminal of said primary winding and one of said input terminals, and (3) a vibratory current interrupter connected between the other of said input terminals and said primary winding to pass cyclically interrupted current through said primary winding upon connection of said terminals to a source of unidirectional voltage, a relay having an operating winding and a pair of contacts adapted to be closed upon energization of said relay, an output network comprising, in series, (1) one of said secondary windings, (2) a rectifier tube havin anode and cathode electrodes and a heater filament for said cathode, and (3) said operating winding, connections from said relay contacts to the terminals of said resistor for shor+-circuiting said resistor upon energization of said relay, and connections from said filament to said other secondary winding.

2. In a system as defined in claim 1, an inductance-capacitance filter circuit in said output network and wherein the inductance element in said filter circuit comprises said relay windin 3. A vibrator-contact protective apparatus for a power supply system of the type comprising a. transformer having a primary and a secondary winding with a vibratory current interrupter connected to cyclically interrupt current flow through said primary winding and an output network including a thermionic rectifier tube connected to said secondary winding to develop a direct current voltage from alternating voltage developed across said secondary winding by said primary current interruption, said protective apparatus comprising a resistor connected in series with said primary winding to limit the current flowing therein, a relay having contacts and having an operating winding connected in circuit with said thermionic rectifier to close said contacts in response to current flow through said relay winding and said rectifier, and connections from said resistor to said contacts to short-circuit said resistor upon closing of said contacts.

4. A power supply system comprising a pair of input terminals adapted to be connected to a source of unidirectional voltage, a transformer having a center-tapped primary winding and a plurality of secondary windings, a resistor, the center tap of said primary winding being connected to one of said input terminals through said resistor, a vibratory current interrupter having a vibratory contact reed connected to the other of said input terminals and having a pair of stationary contacts alternately engaged by said vibratory contact during vibration thereof, said stationary contacts being connected one to each end of said primary winding, a thermionic rectifier tube having an anode and a cathode and having a filament for heating said cathode,

said filament being connected across one of said secondary windings, a relay having operating winding and having contacts arranged to close in response to current flow through said winding, a filter network comprising the series combination of a first capacitor, said relay winding, and a second capacitor, a connection between said cathode and the junction of said relay winding and one of said capacitors, said capacitors each having a terminal connected to said other input terminal, a connection from one terminal of another of said secondary windings to said anode, a connection from another terminal of said another secondary winding to said other input terminal of said voltage source, and connections from said relay contacts to said resistor for shortcircuiting said resistor in response to current fiow through said winding.

5. A power supply system as defin d in claim 4.

including a second transformer having primary and secondary windings, a second resistor connected between a terminal of said second transformer primary winding and one of said input terminals, a second vibratory current interrupter connected between said input terminals and said primary winding to pass cyclically interrupted current through said primary winding upon connection of said terminals to a source of unidirectional voltage, a second pair of contacts associated with said relay and adapted to be closed upon energization of said relay, and connections from said second resistor to said second pair of contacts for short-circuiting said resistor upon closing of said second pair of contacts.

THOMAS P. DILLON.

No references cited. 

